Systems and methods herein generally relate to web printing and more particularly to systems and methods that automatically identify locations of printing defects within printed rolls.
In continuous feed or “web” printing systems, paper (or other printing media) is fed from one roll into a printer, and is output from the printer onto another roll. While such systems offer many advantages, including the ability to transport an entire roll of printed media, when printing faults occur, they cannot be easily located because they are internal to the roll of printed media. In other words, when printing errors happen, the continuous stream of good images on the web is disrupted with bad images.
Depending on the printing error, the web of paper may contain blank frames, defective image frames, partial image frames, or image frames that look good, but are defective because they are behind bad frames. All of this can make determining what frames are good and what frames are bad very difficult, especially if the web is re-rolled up and finished offline in a separate device.
Many times, handwritten notes are added to a completed printed roll to indicate the locations of the good and bad frames to allow subsequent processors to manually cut out the bad frames when the printed roll is unwound for later processing. In addition, the printed roll can be transferred onto another roll and observed (using, for example, automated imaging and comparison systems (based on a known good images)) to locate defective images. However, such systems rely on image analysis to determine if a sheet is good or not, and there can be errors in scanning the roll and this can produce false negatives or false positives. Further, such systems incur the separate time and costs associated with a separate checking step for each printed roll.